Avalanche Forecast

Issued: Apr 23rd, 2023 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

Avalanche Canada jsmith, Avalanche Canada

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Forecast snow and strong southwesterly wind are expected to form fresh wind slabs on lee features at treeline and above.

Concern for triggering large persistent slab avalanches remains. Avoid steep, rocky, and wind-affected areas where triggering slabs are more likely.

Summary

Confidence

Low

Avalanche Summary

Several naturally triggered size 2 wind slab avalanches were reported on northerly aspects in the alpine on Saturday.

A fatal avalanche occurred north of Stewart on April 11th. It was a skier-triggered size 3 persistent slab avalanche that occurred on a northeast aspect in the alpine.

Most professional operations are now closed which means we have very little snowpack or avalanche observation data. Please consider sharing any information or photos you have on the Mountain Information Network to help guide our forecasts.

Snowpack Summary

Forecast snow and strong southwesterly wind are expected to form fresh wind slabs on lee features at treeline and above.

A crust exists up to ridgetop on south-facing slopes and on all aspects up to approximately 1300 m.

The primary concern is two buried weak layers down 40-140 cm deep in most areas. They include facets and surface hoar in shaded areas and a melt-freeze crust elsewhere. Numerous human-triggered persistent slab avalanches have occurred on these layers during the past week.

The mid and lower snowpack is considered generally strong and well-bonded. In the far northern reaches of the region, basal facets may exist which are currently considered inactive. This layer may become active with abrupt changes to the snowpack, such as rapid loading (heavy snowfall or rain) or prolonged warming.

Weather Summary

Sunday Night

Cloudy with flurries; 3-15 cm (rain below 1000 m) / 40 km/h southwest ridgetop wind / Temperature at treeline around -2 C / Freezing level 1100 m

Monday

Cloudy with isolated flurries; 0-10 cm (rain below 1000 m) / 40 km/h southwest ridgetop wind / Temperature at treeline around -3 C / Freezing level 1200 m

Tuesday

Mix of sun and cloud / 20 km/h southwest ridgetop wind / Temperature at treeline around -3 C / Freezing level 1200 m

Wednesday

Mix of sun and cloud with flurries; 5-20 cm (rain below 1000 m) / 60 km/h south ridgetop wind / Temperature at treeline around -2 C / Freezing level 1300 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.

Problems

Wind Slabs

An icon showing Wind Slabs

Forecast snow and strong southwesterly wind are expected to form fresh wind slabs on lee features at treeline and above.

Aspects: North, North East, East, West, North West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs

Numerous large persistent slab avalanches were triggered by riders in the alpine between April 10-12th. Most professional operations are now closed which means we have very little snowpack or avalanche observation data.

The primary concern is a layer of facets and surface hoar buried anywhere from 40-140 cm on shaded slopes. On other slopes, this layer is a crust with facets above. Avoid steep open slopes capable of producing large avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1.5 - 3

Valid until: Apr 24th, 2023 4:00PM

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